@article{ma_wu_hurrey_wallen_grant_2010, title={Sugar Acetates as CO2-philes: Molecular Interactions and Structure Aspects from Absorption Measurement Using Quartz Crystal Microbalance}, volume={114}, ISSN={["1520-6106"]}, DOI={10.1021/jp9122634}, abstractNote={Sugar acetates, recognized as attractive CO2-philic compounds, have potential uses as pharmaceutical excipients, controlled release agents, and surfactants for microemulsion systems in CO2-based processes. This study focuses on the quantitative examination of absorption of high pressure CO2 into these sugar derivatives using quartz crystal microbalance (QCM) as a detector. In addition to the absorption measurement, the QCM is initially found to be able to detect the CO2-induced deliquescence of sugar acetates, and the CO2 pressure at which the deliquescence happens depends on several influencing factors such as the temperature and thickness of the film. The CO2 absorption in α-d-glucose pentaacetate (Ac-α-GLU) is revealed to be of an order of magnitude larger in comparison with its anomer Ac-β-GLU, whereas α-d-galactose pentaacetate (Ac-α-GAL) absorbs CO2 less than Ac-α-GLU due to the steric-hindrance between the acetyl groups on the anomeric and C4 carbons, implying the significant importance of the molecular structure and configuration of sugar acetates on the absorption. The effects of molecular size and acetyl number of sugar acetates on the CO2 absorption are evaluated and the results indicate that the conformation and packing of crystalline sugar acetate as well as the accessibility of the acetyls are also vital for the absorption of CO2. It is additionally found that a CO2-induced change in the structure from a crystalline system to an amorphous system results in an order of magnitude increase in CO2 absorption. Further investigation illustrates the interaction strength between sugar acetates and CO2 by calculating the thermodynamic parameters such as Henry’s law constant, enthalpy and entropy of dissolution from the determined CO2 absorption. Experiments and calculations demonstrate that sugar acetates exhibit high CO2 absorption, as at least comparable to ionic liquids. Since the ionic liquids have potential uses in the separation of acidic gases, it is evident from this study that sugar acetates could be used as possible materials for CO2 separation.}, number={11}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Ma, Shao-Ling and Wu, You-Ting and Hurrey, Michael L. and Wallen, Scott L. and Grant, Christine S.}, year={2010}, month={Mar}, pages={3809–3817} }
 @article{hussain_wu_ampaw_grant_2007, title={Dissolution of polymer films in supercritical carbon dioxide using a quartz crystal microbalance}, volume={42}, ISSN={["1872-8162"]}, DOI={10.1016/j.supflu.2007.03.011}, abstractNote={Abstract The dissolution kinetics of polymeric materials in CO 2 is crucial to the understanding, design and control of CO 2 -based environmentally benign lithography processes. This study utilizes the quartz crystal microbalance (QCM) to monitor and evaluate the dissolution of poly(1,1-dihydroperfluorooctyl methacrylate- r -2-tetrahydropyranyl methacrylate), poly(FOMA- r -THPMA), polymer films in supercritical CO 2 over a range of temperatures and pressures. Polymer dissolution rates at the range of pressures studied were evaluated to quantify the dissolution kinetics for the polymer. The experiments revealed that the polymer dissolution in supercritical CO 2 undergoes two apparent processes: a rapid absorption of CO 2 into the polymer film followed by a gradual dissolution of polymer film into the CO 2 at the polymer–CO 2 interface. The nature of these interfacial phenomena and their associated effect on the rate are discussed.}, number={2}, journal={JOURNAL OF SUPERCRITICAL FLUIDS}, author={Hussain, Yazan and Wu, You-Ting and Ampaw, Paa-Joe and Grant, Christine S.}, year={2007}, month={Sep}, pages={255–264} }
 @article{wu_akoto-ampaw_elbaccouch_hurrey_wallen_grant_2004, title={Quartz crystal microbalance (QCM) in high-pressure carbon dioxide (CO2): Experimental aspects of QCM theory and CO2 adsorption}, volume={20}, ISSN={["0743-7463"]}, DOI={10.1021/la035502f}, abstractNote={The quartz crystal microbalance (QCM) technique has been developed into a powerful tool for the study of solid-fluid interfaces. This study focuses on the applications of QCM in high-pressure carbon dioxide (CO2) systems. Frequency responses of six QCM crystals with different electrode materials (silver or gold) and roughness values were determined in helium, nitrogen, and carbon dioxide at 35-40 degrees C and at elevated pressures up to 3200 psi. The goal is to experimentally examine the applicability of the traditional QCM theory in high-pressure systems and determine the adsorption of CO2 on the metal surfaces. A new QCM calculation approach was formulated to consider the surface roughness contribution to the frequency shift. It was found that the frequency-roughness correlation factor, Cr, in the new model was critical to the accurate calculation of mass changes on the crystal surface. Experiments and calculations demonstrated that the adsorption (or condensation) of gaseous and supercritical CO2 onto the silver and gold surfaces was as high as 3.6 microg cm(-2) at 40 degrees C when the CO2 densities are lower than 0.85 g cm(-3). The utilization of QCM crystals with different roughness in determining the adsorption of CO2 is also discussed.}, number={9}, journal={LANGMUIR}, author={Wu, YT and Akoto-Ampaw, PJ and Elbaccouch, M and Hurrey, ML and Wallen, SL and Grant, CS}, year={2004}, month={Apr}, pages={3665–3673} }
 @article{burns_wu_grant_2003, title={Mechanisms of calcite dissolution using environmentally benign polyaspartic acid: A rotating disk study}, volume={19}, ISSN={["0743-7463"]}, DOI={10.1021/la020815g}, abstractNote={The removal of calcium mineral deposits from metal surfaces is of practical interest for a variety of fields (i.e., food, petroleum, and chemical industries). This study investigated the mechanisms of calcite (CaCO3) dissolution using environmentally benign polyaspartic acid (PASP) under controlled hydrodynamic conditions by a rotating disk technique. The specific role of PASP conformation and surface interactions in the dissolution process was further studied using scanning electron microscopy and dynamic light scattering techniques. Using this combined approach, the dissolution mechanisms were investigated as a function of pH (3.5−10.0), rotating speed (150−1500 rpm), polymer concentration (0.001−0.1 M), and molecular weight (3000 and 10 000 Mw). To quantify the effect of PASP on enhancing calcite dissolution, an enhancement factor, ηenh, was defined as a ratio of the rate of dissolution in PASP over the rate in water. Maximum enhancement was observed at pHs in the range 4−5, where an optimal combinatio...}, number={14}, journal={LANGMUIR}, author={Burns, K and Wu, YT and Grant, CS}, year={2003}, month={Jul}, pages={5669–5679} }
 @article{wu_grant_2002, title={Effect of chelation chemistry of sodium polyaspartate on the dissolution of calcite}, volume={18}, DOI={10.1021/la0118939a}, number={18}, journal={Langmuir}, author={Wu, Y. T. and Grant, Christine}, year={2002}, pages={6813–6820} }